In recent years, the miniaturization and the trends towards a finer pitch of wiring in a semiconductor component have been advancing. For that reason, a substrate container to store a semiconductor wafer (a precision substrate) is required to have a high hermeticity and the automization of handling in order to prevent the precision substrates from being contaminated. As such a substrate container, a substrate container equipped with a check valve used on the occasion of gas purge (for example, refer to Patent Documents 1 to 3) is known.
FIG. 16 is an exploded perspective view showing a check valve in a conventional substrate container. As shown in FIG. 16, in a conventional substrate container, a through-hole 51a is formed on a wall 51 of the container main body in which substrates are contained and a check valve 52 used on the occasion of gas purge is mounted in the through-hole 51a. The check valve 52 is provided with a valve disc 53 having an annular sealing face and a cylindrical housing 54 to contain the valve disc 53. The housing 54 has a retaining cylinder 55 installed on the inner face side of the container main body and a fixing cylinder 56 installed on the outer face side of the container main body and threads 55a and 56a are formed on the outer face side of the retaining cylinder 55 and on the inner face side of the fixing cylinder 56, respectively. Then the retaining cylinder 55 and the fixing cylinder 56 are placed in the manner of interposing the wall 51 in between and, by screwing them together, the housing 54 is formed and fixed to the wall.    Patent Document 1: Japanese Patent Application Laid-open No. 2004-146676    Patent Document 2: Japanese Patent Application Laid-open No. 2004-179449    Patent Document 3: Japanese Patent Application Laid-open No. 2002-521189